1. Field of the Invention
The present invention is in the field of automotive mechanics and specifically relates to a tool for installing valve locks on a valve stem. The valve lock removably secures a valve retainer to the valve stem. The tool typically would be used by an automobile mechanic or by an engine reconditioner.
2. The Prior Art
During the compression and expansion cycles, the valves of a conventional internal combustion engine are forced shut by the high pressure within the cylinder. To implement the intake and exhaust cycles, the valves must be opened at appropriate times, and this is usually accomplished by the use of a cam that pushes against the end of the valve stem, thereby forcing the head of the valve into the combustion chamber. To assure positive operation, a valve spring urges the valve to its closed position, and the cam must overcome the urging of the valve spring to open the valve. Typically, the valve spring is a compression spring. One end of the compression spring bears against a stationary part of the engine, and the other end of the spring bears against a valve spring retainer that is removably secured to the valve stem by a valve lock. Were it not for the valve lock, the compressive force of the valve spring would push the retainer off the end of the valve stem. The retainer must be removably secured to the valve stem to permit assembly and dis-assembly of the valve.
In theory, a nut and washer would suffice to secure the retainer to the valve stem. However, after nearly a century of experience, a specialized type of valve lock is almost universally used. The retainer has a tapered central bore that opens toward the end of the valve stem. The valve stem has an end portion that includes a circumferential groove. The valve lock is a tapered split collar that has an inwardly facing ridge. The ridge engages the circumferential groove of the valve stem and is held in engagement by the taper of the central tapered bore of the retainer. The valve lock is thus jammed between the circumferential groove on the valve stem and the tapered central bore of the retainer, which is urged toward the end of the valve stem by the valve spring.
Although this way of securing the retainer to the valve stem is simple and effective in use, it has proven to be very challenging for most mechanics to take apart and reassemble, which must be done when the valves are ground or the engine is reconditioned.
Part of the difficulty is that the retainer must be drawn back, away from the end of the valve stem against the urging of the valve spring, to expose the valve locks. In contemporary engines, the force exerted by the valve spring is in the range of 60 to 90 pounds, and mere finger pressure generally is not adequate. Another part of the difficulty is that the valve locks are rather small in comparison to the valve stem and are difficult to manipulate. To make matters worse, the valve spring and the retainer are frequently located in a poorly-illuminated and fairly close-fitting recess, which makes the parts somewhat inaccessible.
Large console-type machines are commercially available, but they merely compress the valve springs. They occupy valuable floor space in the shop, and have a high initial cost. It appears that a need exists for a hand tool to facilitate the installing of valve locks.
The present invention is a hand tool to facilitate the installation of a valve lock into a circumferential groove on a valve stem.
In accordance with the present invention, the tool includes a loader end cap having an end that faces the valve spring retainer when the tool is in use and further includes a central bore extending in the direction of the axis of the valve stem when the tool is in use. A plunger extends through this bore and protrudes beyond the end of the loader end cap. The plunger is biased toward the valve stem and has the same diameter as the valve stem. The valve locks are placed by the user on the protruding cylindrical surface of the plunger, and the axis of the plunger is brought into alignment with the axis of the valve stem. The user then pushes the tool against the valve spring retainer, gradually depressing the retainer by compressing the valve spring, and the end of the valve stem makes contact with the protruding end of the plunger. As the tool is pushed onto the valve stem, the valve stem forces the plunger back into the loader end cap, and the valve locks are pushed onto the valve stem by the loader end cap. The valve locks engage the circumferential groove on the end portion of the valve stem, and as the tool is withdrawn, the retainer advances toward the end of the valve stem also engaging the valve locks and preventing them from coming out of the circumferential groove.
The tool of the present invention permits the valve locks to be installed in a valve in approximately 15 seconds per valve, which is one-third to one-quarter of the time previously required, depending on the mechanic. The hand tool of the present invention occupies no floor space in the shop, and costs only about one-tenth of the cost of the large console-type machines currently on the market.
The operation of the tool as well as its construction will be described in detail in the following paragraphs with the help of the accompanying drawings. The drawings show a preferred embodiment of the invention, but should not be regarded as limiting the scope of the invention.